State and municipal water departments flush water mains and water hydrants routinely as part of a regular maintenance program or when commissioning new construction, for example in a new subdivision, as water pressure and pipes are being tested and prepared for use. Flushing involves actuating hydrant valves to “full open” position so that maximum water flow will be allowed in order to achieve maximum efficiency of the maintenance or commissioning process.
Water hydrants are typically located along street curbs in areas where access to the hydrant could become necessary (e.g. for emergency use by fire departments), largely in residential or commercial neighbourhoods, although they can be mounted in various other locations. The hydrants are constructed to generally produce a high volume of water discharge, with sufficient pressure and kinetic energy to exert a potentially damaging force upon any object which might come into its path. Further, water flow from the hydrant valve will exit in a fixed direction from the hydrant, without any ability to control the direction of discharge. As a result, flushing water hydrants can pose a serious safety issue to any nearby objects and passing pedestrian or vehicular traffic, particularly in residential neighbourhoods. To minimize such risk, water hydrant flushing will involve blocking traffic and the presence of personnel to protect the immediate vicinity of the hydrant.
In addition to safety concerns, the high pressure flow from a full open hydrant can cause environmental damage to landscaping in the output path of the flow. The result can be unsightly and costly landscaping repairs, washout erosion damage, and sediment build up in the water system (i.e. pollution).